Sorption vessel with internal interstage screening vessel

ABSTRACT

A sorption vessel including a tank for retaining a pulp of an aqueous slurry and a sorbent at a predetermined liquid pulp level therein; and an interstage screening system disposed within the tank and at least partially submerged beneath the predetermined pulp level. The interstage screening system includes a housing for isolating the system from the pulp, thereby providing a hydraulic differential between the predetermined pulp level and the screening system; a conduit for selectively introducing the pulp onto the screen member, the pulp being urged through the conduit by the hydraulic differential; and at least one screen member disposed within the housing for selectively and continuously separating the sorbent from the pulp.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sorption vessel having an internalinterstage screening system. The sorption vessel of this invention hasparticular utility for sorbing gold values from a slurry containing thesame.

2. Description of the Background Art

Precious metals, such as gold and silver, and other metals, such ascopper, iron and nickel, are typically contained in ore materials whenmined. Metal-containing ores are typically processed in accordance withone or more known techniques so that the metals, especially preciousmetals, can be separated and extracted from the mined ore.

One known method of recovering precious metals or other metals frommetal-containing ores occurs in a carbon-in-pulp system whereinactivated carbon, usually in the form of activated charcoal, is mixedwith a slurry of the ore in a cyanide solution. The carbon remains incontact with the slurry for a time sufficient to permit the gold andsilver to become adsorbed by the carbon and, thereafter, the carbon isseparated from the residue, typically by some type of interstage screenassembly. The carbon particles are generally larger than the finelyground ore particles which permits the screening step to be accomplishedwith relative ease. A carbon-in-pulp system utilizes a plurality ofmechanically or pneumatically agitated tanks arranged in series, usually4 to 6. Each tank generally contains activated carbon having a differentamount of gold adsorbed thereon; with the first tank having the highestand the last tank having the lowest. A slurry of a finely ground ore andthe alkaline cyanide metal complex solution, is introduced into thefirst tank, while the carbon is advanced countercurrently to the flow ofslurry from the last tank to the first tank. The slurry is agitated withthe carbon adsorbent in the tank and the carbon adsorbs the cyanidemetal complex as the slurry and the carbon adsorbent, i.e., the pulp, isagitated. The pulp is sequentially passed through the series of thepneumatically or mechanically agitated tanks so that most of the cyanidemetal complex is adsorbed by the carbon.

After passing through the series of tanks, the processed tailings arediscarded. As stated above, the carbon containing the adsorbed cyanidemetal complex can be sequenced through the tanks in reverse order fromthe ore slurry. After the adsorbent has passed completely through thesystem, it has become "loaded" with the adsorbed metal complex. Theloaded adsorbent is then chemically processed to remove most of themetal. The stripped adsorbent is then reactivated and then returned tothe carbon-in-pulp system.

Another known method of recovering metals from metal-containing oresoccurs in a carbon-in-leach system. The carbon-in-leach system issimilar to the carbon-in-pulp system. The primary difference between thecarbon-in-pulp system and carbon-in-leach system is that in the former,there are mixing tanks for cyanidation leaching prior to the carbonadsorption stage. In a carbon-in-leach system, cyanidation is conductedin the presence of carbon.

A further method of recovering metals from metal-containing ores occursin a resin-in-pulp system. Generally, in a resin in pulp system, aleached metal-containing ore pulp is exposed to a resin, typicallyemployed as moderately coarse particles, in a series of agitator tanks.The particular resin is, thereafter, separated from the pulp with themetal complex adsorbed thereon and, ultimately, the metal complex isremoved from the resin to recover quantities of the particular metalpresent in the ore.

A detailed review of the screening systems currently in use forseparating either the carbon or resin adsorbents from the slurry of apulp can be found in the following art: P. A. Laxen, "Interstage ScreensOn The Adsorption Circuit of An `In-Pulp` Process" and Gold & SilverRecovery Innovations, "CIP Interstage Screens", Phase III, Vol. 7, Ch.42, pp. 4079-4184. Initial carbon-in-pulp ("CIP") plants utilizedexternal vibrating screens over which the pulp with entrained carbon waspumped by air lifts from the bottom of the adsorption tanks. Each tankutilized a number of external vibrating screens to which external airlifts on the side of each tank lifted pulp plus carbon onto the screens.The screen pulp would flow by gravity to the next tank while the carbonon the screen flows back to the tank from which it came exceptperiodically when it is diverted to the next tank countercurrent to thepulp flow. The disadvantages associated with this type of system include(1) the capital cost of external vibrating screens, air lifts andcompressors for air supply; (2 ) additional costs of supportingstructures for the screens; (3) compressed air and screen maintenanceare relatively high for a large scale plant with the system being muchmore energy intensive than it needs to be; (4) the large amount of airinjected into the pulp results in substantial carbon scaling; (5) theefficiency of the system is low since a portion of the carbon iscontinuously not in contact with pulp and therefore not absorbing metalvalues therefrom; and (6) excessive operator manpower required on largeplants for monitoring the system for ruptures and/or replacement of thescreen media.

To upset these disadvantages, systems have been installed which utilizeboth external and internal screens, with the external screens being usedfor carbon transfer only. The majority of the pulp (about two-thirds)flows to internal air cleaned screens while the remainder of the pulp iscontinuously pumped by a submergible pump to the external screens withthe carbon either being returned to the leach tanks or transferred tothe next tank as required for countercurrent carbon transfer. The pulpfrom the external screen, again one-third of the total, flowscontinuously to the next tank.

In about 1982, a new type of screen evolved, these known has the EPAC(equal pressure air cleaned) screens. By damming the pulp flow on thedownstream side of the screen, the hydrostatic pressure is equalized onboth sides of the screen and is not as readily blinded by carbonparticles pinned to the screen surface. This simple technique increasesthe screen capacity of a screen panel per unit of length by a factor of10 or more. An illustration of this type of screen is shown in U.S. Pat.No. 2,808,928. A wide variety of types, sizes and configurations of EPACscreens is known in the prior art. Each of these systems has its ownattendant disadvantages mostly relating to the difficulties in keepingthe screen clean of carbon build up along with the difficulties ofachieving high throughput. In addition, the quantities of air requiredand the operational aspect for use of such air create furtherdisadvantages for this type of system.

One improvement on the EPAC screens is known as KAMBALDA screens. Thesescreens were able to dispense with the air cleaning system by mountingthe screen horizontally in an upper portion of the tank and byinstalling an agitator blade beneath the screen in a manner such thatpulp is directed against the screen with the agitation caused by theblades continually moving the carbon away from the screen to preventbuild up. The screened pulp is removed from the top of the tank and isintroduced into the subsequent tank in the lower portion thereof withthe mixture in the second tank causing the pulp to flow upwardly andonto the next screen. The agitator blade is known as a sweeper arm andis mounted a few inches away from the bottom of the screen. While thetotal energy requirements for this type of screen is less thanconventional EPAC screens, the disadvantages for this system relate tothe extensive amount of structural steel required above the tank tosupport the agitator with its sweeper, as well as the screens locatedthereabove.

Another improvement on the EPAC screens was made at North Kalgurli Minesand is known as the NORKAL screen. This screen consist of a cylindricalscreen basket along with pedals which rotate along its circumference tosweep away carbon build up. Screened pulp flowing into the cylindricalscreen basket is drained through an out-flow and is directed to the nexttank. The improvement of this type of arrangement relates to an increasein throughput with a corresponding decrease in energy necessary toachieve that throughput. The disadvantages of such a system are similarto those identified above for the KAMBALDA screens.

As noted in the articles cited above, the shortcomings associated withknown interstage screening installations are their energy intensiveoperational requirements, which are predominantly ascribed to thecompressed air requirements; the high maintenance and operational costs,since, in order to advance the adsorptive species on a continuous orsemi-continuous basis, as is necessary, the internal launder ormechanical interstage screening system must pump the total pulp (i.e.,slurry and carbon); the low throughput per unit area; and the absence ofany separation or concentration of the adsorptive species from the pulp.Additionally, due to the abrasive nature of the adsorptive species, theconventional wire or cloth interstage screens have a relatively shorteffective life which necessitates constant inspection and replacement,else the adsorptive species and, hence, the adsorbed metals, remain inthe pulp and cannot be recovered.

Other problems associated with prior art installations relate to carbontransfer pumps used in such installations and, more specifically, thedeleterious effect they have on the sorbent.

SUMMARY OF THE INVENTION

The invention relates to a sorption vessel including a tank for holdinga pulp including an aqueous slurry and a sorbent, the pulp beingmaintained at a predetermined level in the tank, and a screening systemdisposed with the tank and being at least partially submerged beneaththe predetermined pulp level. The screening system includes a housingfor isolating the screening system from the pulp, thereby providing ahydraulic differential between the predetermined pulp level and thescreening system; at least one screen member disposed within the housingfor selectively and continuously separating the sorbent from the slurry;and means for directing the pulp onto the screen member as the pulp isdisplaced towards the screening system by the hydraulic differential.

This vessel may utilize a pump for removing one of the sorbent or thepulp from the tank. Also, means for agitating the pulp may be used tofacilitate contact between the sorbent and the slurry, therebyincreasing the degree of sorption of metal values from the slurry by thesorbent. Advantageously, the vessel has means for introducing one ofadditional slurry or additional sorbent thereinto the vessel to maintainthe pulp at its predetermined level.

In one embodiment, the screening system generally includes a pluralityof screen members which are angularly disposed in the housing withrespect to the predetermined pulp level, with the screening having meansfor vibrating the screen members to facilitate separation of the sorbentfrom the slurry. Alternatively, the screen member may comprise acontinuous linear screen. In either case, the pulp directing meansfurther utilizes a valve means for selectively introducing pulp into thescreening system, and the tank includes at least one baffle to assist inthe direction of movement of the pulp in the tank. If desired, aplurality of screening systems can be used.

A preferred embodiment of the pulp directing means is a conduit, one endof which extends to a lower portion of the tank and directs the pulp tothe screening system. The opposite end of the conduit may include adistribution box member for uniformly distributing the pulp into thescreening system. The separated slurry removing means generallycomprises a drainage member extending from a lower portion of thescreening system housing through a wall of the tank.

The vessel itself may utilize means for agitating the pulp to facilitatecontact between the sorbent and the aqueous slurry, thereby increasingthe degree of sorption of metal values from the slurry by the sorbent.The vessel may also include means for introducing additional slurry,preferably into an upper portion of the tank, while one or more spargersmay be used to introduce air into the pulp.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one vessel used in accordance withthe present invention;

FIG. 2 is a side view of the interstage screening system used inaccordance with the present invention with the internal structuralcomponents thereof being exposed and illustrating pulp disposed therein;

FIG. 3 is a schematic representation of the cooperative arrangement ofthe interstage screening system and the pump of the present invention;

FIG. 4 is a perspective view of the pump of the present invention with aportion cut away to expose the agitation means; and

FIG. 5 is a side view of the pump of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The general process of recovering gold from a gold bearing ore employinga combined cyanidation and adsorption treatment is described in U.S.Pat. No. 4,188,208, the entire content of which is incorporated hereinby reference. While the description in that U.S. Patent relatesparticularly to gold recovery, as does the description providedhereinbelow, the underlying theory is used in processes for recoveringsilver, iron, copper, nickel and other metals. The recovery of each ofthese metals from a mined ore is within the scope of the presentinvention.

An aqueous slurry is prepared by grinding a crushed metal-containing oreto about 50% to about 70% minus 200 mesh and mixing the ground ore witha sufficient amount of water so that it forms a slurry with about 40 toabout 50% solid in water. Alternatively, the ore can be wet grinded toform the slurry. Preparation of the slurry in this manner is offered asan illustration; however, any of the particular techniques for formingthe slurry which are known to those skilled in the art are available foruse and are contemplated by the method of this invention.

The ore may optionally be subjected to oxidation treatment prior tocyanidation treatment to enhance the quantities of metal recovery byemploying any pre-oxidation technique known to those skilled in the art.

The slurry is then treated with a substance, such as cyanide, and in amanner such that a metal complex is formed between the particularsubstance used for treating the slurry and the metal present in the ore,which metal complex is capable of being adsorbed by the particularadsorbent employed. For purposes of this description, a method forrecovering gold from a gold-bearing ore in a carbon-in-pulp installationis described. It is to be fully understood, however, that the method andsystem of this invention are applicable to the recovery of other metalsin carbon-in-pulp, carbon-in-leach and resin-in-pulp installations. Ofcourse, appropriate substitutions of components which are apparent tothose skilled in the art must be considered and, if necessary,implemented. Thus, in a process for recovering gold from an orecontaining the same, the gold is leached from the slurry in the form ofa cyanide complex, specifically, an aurocyanide complex. For instance,sodium hydroxide and sodium cyanide, or potassium hydroxide andpotassium cyanide, are added to the aqueous pulp in amounts such thatthe pulp contains from about 0.1 to 10% by weight of lime or an alkalimetal hydroxide and from about 0.1 to 1.0% by weight of the alkali metalcyanide. In addition, up to about 10% by weight of sodium carbonate orpotassium carbonate may also be added to the pulp. A resulting cyanidecomplex is produced which can be adsorbed by certain adsorbent solids,such as, activated carbon.

The adsorptive properties of activated carbon are ascribed to its largeinternal surface area, its pore size distribution, and the externalsurface area. Activated carbon functions by adsorption due to theimbalance of the forces upon the carbon atoms constituting the surfaceof the pore walls. Carbon is generally selective for gold and silvercyanide complexes, however, other complexes of copper, iron or nickelmay be adsorbed. The carbon can be obtained from any conventionalsource, such as, for instance, dense woods, nut shells, fruit pits orcoke derived from anthracite coal or petroleum products, and can beactivated in any conventional manner. Preferably, the carbon is soakedin water having a pH of about 11 for at least about 4 hours prior tobeing added to the pulp. For reasons explained hereinbelow, the size ofthe carbon particulate should be greater than the size of the pores ofthe screen employed in the interstage screening phase. It is thereforepreferably to employ carbon particulate having a mesh size of about 6 toabout 16.

While the method of the present invention may be practiced in one stage,that is, in one tank or vessel, it can be practiced in a plurality oftanks arranged in series, with each tank having one or more interstagescreening systems. Preferably, the invention is carried out in 4 to 6tanks, with the most preferred being a 6 tank arrangement.

Accordingly, the following description relates to a single sorbentvessel of the present invention, it being fully understood, however,that two or more of the described vessels may be used in accordance withthis invention.

Referring now to the drawings, particularly to FIG. 1, illustrated isthe sorption vessel of the present invention, which is generallydesignated as reference numeral 10. Sorbent vessel 10 includes a tank 12which includes the slurry described hereinabove and a sorbent, such as,the activated carbon described above. The admixture of aqueous slurryand sorbent will hereinafter be referred to as a pulp. It is to befurther understood that the slurry includes the cyanidation reagent.Inasmuch as slurry is continuously introduced into tank 12 via slurryentry means 14 and further since sorbent is continuously introduced intotank 12 at the proximity of arrow A the pulp is maintained in the tankat a predetermined level, which level is represented as referencenumeral 16. Although not shown, slurry entry means 14 can be a downcomerwhich has a first end proximate or associated with a source of theslurry and a second end disposed within tank 12.

Sorption vessel 10 further includes agitation means 18 which, whenactuated, agitates the pulp to facilitate contact between the sorbentand the slurry, thereby increasing the degree of sorption of metalvalues from the slurry by the sorbent. In a preferred embodiment,agitation means 18 includes a rotatable shaft 20 and two impeller blades22a, 22b associated therewith. It is to be understood, however, thatother agitation means may be employed to facilitate contact between thesorbent and the slurry.

Sorption vessel 10 can optionally include one or more baffles 25 todirect the movement of the pulp within the tank to desired locations.Also, a sparge pipe 27 can be used to introduce air or other oxidizingagent into the slurry for proper operation of the process, as will bemore clearly understood from the description provided below.

Sorption vessel 10 further includes a screening system 24 that isdisposed within tank 12. Referring now to FIG. 2, screening system 24 isillustrated in greater detail and, as shown, is at least partiallysubmerged beneath the predetermined pulp level 16. The extent to whichscreening device 24 becomes submerged in the pulp is determined by theliquid level of the pulp and the amount of pulp introduced intoscreening device 24. Screening system 24 isolate pulp disposed thereinfrom the pulp contained within tank 12 by way of a housing 26, whichprovides a hydraulic differential between the predetermined pulp level16 and screening system 24. As pulp is continuously introduced intoscreening system 24, sorbent is selectively and continuously separatedfrom the slurry by way of screen members 28. Screen member 28 caninclude one or more individual screen panels or, alternatively, screenmember 28 can include a continuous linear screen, such as, for example,the one illustrated in U.S. Pat. No. 4,692,240, the entire content ofwhich is incorporated herein by reference. In a most preferredembodiment, screen member 28 is angularly disposed with respect to pulplevel 16. Preferably, screen 28 is vibrated by vibration means, such asthe dual motor arrangement 30. However, a single motor arrangement isalso within the scope of this invention. Motors 30 can also be used toimpart motion to a continuous linear screen in the event that such anembodiment is opted for.

Screen member 28 has openings ranging in size, for example, from about0.1 mm to about 1 mm, with a preferred size of 0.7 mm for separatingactivated carbon in a CIP installation. Screen member 28 is mostpreferably fabricated from urethane to avoid the abrasive effect ofcarbon particulate.

Screening system 24 has developed from this technology and now isavailable from Derrick Manufacturing Corporation, Buffalo, N.Y. as theirFlow Line Cleaner.

Referring once again to FIG. 1, sorption vessel 10 further includesmeans for directing pulp onto screen member 28, whereby the pulp isdisplaced toward screening system 24 and, hence, screen member 28 by wayof the aforedescribed hydraulic differential. For instance, the meansfor directing the pulp can include conduit means such as upcomer 32. Asillustrated, upcomer 32 has a lower end disposed within tank 12 at aposition below pulp level 16, preferably at the bottom portion of tank12, and further has an upper end disposed within the proximity ofscreening system 24. Alternatively, a baffle (not shown) can be used todirect pulp into screening system 24. The degree of pulp to be directedonto screen member 28 can be regulated by a feed weir 34 as shown inFIG. 3, it being understood that feed weir 34 can preclude entry of pulpinto screening system 24 or can permit entry of pulp by way of valve 36,associated with feed weir 34, which permits the opening and closing offeed weir 34.

Conduit means 32 can further include a distribution box 33 associatedwith the upper portion thereof and within the proximity of screeningsystem 24 to uniformly distribute pulp into screening system 24.

Additionally, tank 12 can be provided with one or more spargers (notshown) for introducing air into the pulp for reasons well understood bythe skilled artisan.

Referring to FIG. 3, sorption vessel 10 can further include a pump 38for removing sorbent and/or pulp from tank 12 via screening system 24.Referring now to FIGS. 3 to 5, pump 38, which is a vertical pump,includes an upper chamber 40 for receiving pulp or, for that matter, anytype of solid-liquid dispersion. Upper chamber 40 includes an opening atthe top thereof and an opening at the bottom portion to provide fluidcommunication between upper chamber 40 and intermediate chamber 42.Upper chamber 40 further includes a conduit or nozzle 43 for directingliquid into pump 38 for forming a dispersion with the solid particulateintroduced therein which liquid can be stored in reservoir 41. Upperchamber 40 can further include a second conduit 46 for intermittentlydelivering solids into upper chamber 40. In a most preferred embodiment,pump 38 is provided with a piston 48, as is best seen in FIG. 3, whichprovides relative motion between a position adjacent screen system 24and a position removed from the adjacent position whereby solids areprevented from entering upper chamber 40. Movement of pump 38 betweenthese positions is facilitated by flanged wheels 45, 47 rotatablyattached to pump 38 by axles 44, 46. Two sets of wheels 45, 45a and 47,47a are provided on each side of pump 38 as shown in FIG. 3, for rollingmovement along a structural beam or rail (not shown). Piston 48 can beeither mechanically or pneumatically actuated to move pump 38 to andfrom the aforedescribed positions. With this arrangement, solids can bedelivered directly into reservoir portion 41 by sliding down ramp 29 ofscreening system 24.

As seen in FIG. 4, intermediate chamber 42 further includes a dischargeconduit 50 for discharging the dispersion from pump 38. Still referringto FIG. 4, pump 38 further includes a lower chamber 52 which is in fluidcommunication with intermediate chamber 42. Lower chamber 52 furtherincludes means for inducing a vortex in intermediate chamber 42, such asagitator 54. Agitator 54 further includes impeller blades 56a, 56b whichare disposed within lower chamber 52. Rotation of impeller blades 56a,56b within lower chamber 52 induces a vortex within intermediate chamber42 and which precludes solids from entering lowering chamber 52 andwhich further causes the solids to be discharged out of pump 38 throughdischarge conduit 50. In accordance with this arrangement any solids,such as the carbon sorbent used in accordance with the present inventionare discharged from pump 38 without being deleteriously affected,inasmuch as the solids are transferred from the pump without ever makingcontact with impeller blades 56a, 56b.

In a preferred embodiment intermediate chamber 42 includes a curvedouter-crossed sectional portion 58 to facilitate the formation androtation of the vortex and discharge conduit 50 is tangentially disposedwith respect to curved portion 58.

In accordance with the method of the present invention, which is bestappreciated by collectively referring to FIGS. 1, 2, and 3, slurry isfirst introduced into tank 12 via slurry entry means 14. Sorbent isintroduced into tank 12 in any conventional manner, but is preferablyintroduced at the locus at arrow A, to create a pulp within tank 12 andfurther to enable the sorbent to contact the slurry.

Metal values are sorbed from the slurry in tank 12 by mixing the pulp,such as by actuating agitation means 18, which assures homogeneitybetween the sorbent and the slurry and which substantially uniformlydistributes the sorbent throughout the slurry, thereby facilitating thesorption of the aurocyanide complex by the sorbent. Because of thecontinuous introduction of slurry via slurry entry means 14 accompaniedby continuous introduction of sorbent, pulp level 16 is substantiallymaintained at all times.

A portion of the pulp is directed into screening system 24 where itbecomes isolated from the pulp remaining in tank 12. After having beenpassed over screen member 28 the sorbent, now impregnated with metalvalues, is separated from the slurry by moving upwardly along the screenmember 28 due to the vibration imparted thereto by motors 30a and 30b.The slurry of the pulp passes through the screen openings while thecarbon sorbent is retained upon the screen member 28. The vibrationurges the sorbent to move upwardly along the screen to ramp 29, where itcan slide back into the pulp in tank 12 by the force of gravity.

The separated sorbent is returned into tank 12 on a substantiallycontinuous basis for further adsorption; however, any portion of thesorbent can be removed from the screening system so that the metalvalues may be desorbed therefrom or to transfer the sorbent to anothertank. It is most preferable to primarily return the separated sorbentinto tank 12, while intermittently removing the portion of the sorbentfrom screening system 24. This is accomplished by urging the sorbentalong screen member 28 in the manner hereinbefore described, and out ofscreening system 24 while pump 38 is advanced from a position removedfrom screening system 24 to a position proximate to the screening systemso that the sorbent can be introduced into pump 38 sliding down ramp 29due to the force of gravity for direct introduction into reservoir 41.

During the step of separating the sorbent from the slurry, the slurrypasses through screen member 28, accumulates within housing 26 where itcontinues to remain isolated from the pulp in tank 12. The isolatedslurry is removed from housing 26 by way of conduit means, such as pipe60 and is preferably directed to a downstream tank for furthertreatment, which tank is in fluid communication with the upstream tankvia pipe 60. Alternatively, when the gold values have been substantiallyadsorbed from the slurry, the slurry can be directed to a storage area,typically referred to as a tailings pond by those skilled in the art.

As the slurry is directed to one or more downstream vessels, the amountof metal values associated with the slurry is reduced inasmuch as themetal values are continuously being adsorbed therefrom. Accordingly, theamount of metal values associated with the sorbent is increased in eachof the vessels as it is simultaneously directed therethrough.

In a preferred embodiment, sorbent is countercurrently directed throughthe vessels with respect to the advancement of slurry therethrough and,as such, the amount of metal values sorbed by the sorbent increases asit is countercurrently advanced from the last tank of the series in aupstream direction toward the first tank.

What is claimed is:
 1. A sorption vessel comprising:a tank for holding apulp including an aqueous slurry and a sorbent, said pulp beingmaintained at a predetermined level in said tank; means for separatelyintroducing each one of pulp, slurry and sorbent into said tank; ascreening system disposed with said tank and being at least partiallysubmerged beneath said predetermined pulp level for creating a hydraulicdifferential between said screening system and said predetermined pulplevel, said screening system comprising:(a) a housing for isolating saidsystem from fluid contact with said pulp, and comprising means forproviding said hydraulic differential between said predetermined pulplevel and said screening system; (b) means for directing said pulptowards said screening system by said hydraulic differential; and (c)means disposed within said housing for selectively and continuouslyseparating said sorbent from said slurry.
 2. The vessel of claim 1further comprising a pump for removing one of said sorbent or said pulpfrom said tank.
 3. The vessel of claim 1 further comprising means foragitating said pulp to facilitate contact between said sorbent and saidslurry, thereby increasing the degree of sorption of metal values fromsaid slurry by said sorbent.
 4. The vessel of claim 1 further comprisingmeans for introducing said separated sorbent into said tank.
 5. Thevessel of claim 1 wherein said sorbent separating means includes aplurality of screen members which are angularly disposed in said housingwith respect to said predetermined pulp level.
 6. The vessel of claim 5wherein said screening system includes means for vibrating said screenmembers to facilitate separation of said sorbent from said slurry. 7.The vessel of claim 1 wherein said sorbent separating means comprises acontinuous linear screen to facilitate separation of said sorbent andsaid slurry from said pulp.
 8. The vessel of claim 1 wherein the pulpdirecting means further comprises valve means for selectivelyintroducing pulp into said screening system.
 9. The vessel of claim 1wherein said tank includes at least one baffle to assist in thedirection of movement of said pulp in said tank.
 10. A sorption vesselcomprising:a tank for retaining a pulp of an aqueous slurry and asorbent at a predetermined pulp level therein; means for separatelyintroducing each one of pulp, slurry and sorbent into said tank; ascreening system disposed within said tank and at least partiallysubmerged beneath said predetermined pulp level for creating a hydraulicdifferential, said screening system comprising:(a) a housing forisolating said system from fluid contact with said pulp, and comprisingmeans for providing said hydraulic differential between saidpredetermined pulp level and said screening system, (b) means disposedwithin said housing for selectively and continuously separating saidsorbent from said slurry; and (c) a conduit for selectively introducingsaid pulp into said screening system, said pulp being urged through saidconduit by said hydraulic differential.
 11. The vessel of claim 10wherein a plurality of screening systems are included in said tank. 12.The vessel of claim 10 further comprising a pump for removing one ofsaid sorbent or said pulp from said tank.
 13. The vessel of claim 10wherein the sorbent is active carbon.
 14. The vessel of claim 10 whereinsaid sorbent separating means comprises a continuous linear screen tofacilitate separation of said sorbent and said slurry from said pulp.15. The vessel of claim 10 further comprising means introducingadditional slurry into an upper portion of said tank.
 16. The vessel ofclaim 10 further comprising one or more spargers for introducing airinto said pulp.
 17. The vessel of claim 10 further comprising means foragitating said pulp to facilitate contact between said sorbent and saidaqueous slurry, thereby increasing the degree of sorption of metalvalues from said slurry by said sorbent.
 18. The vessel of claim 17wherein one end of said conduit extends to a lower portion of said tankand directs said pulp to said screening system.
 19. The vessel of claim18 wherein the opposite end of said conduit includes a distribution boxmember for uniformly distributing said pulp into the screening system.20. The vessel of claim 10 wherein said sorbent separating meansincludes a plurality of screen members which are angularly disposed insaid housing with respect to said predetermined pulp level.
 21. Thevessel of claim 20 wherein said screening system includes means forvibrating said screen members to facilitate separation of said sorbentfrom said slurry.
 22. A sorption vessel comprising:a tank for retainingpulp of an aqueous slurry and a sorbent at a predetermined pulp leveltherein; means for separately introducing each one of pulp, slurry andsorbent into said tank; a screening system disposed within said tank andat least partially submerged beneath said predetermined pulp level forcreating a hydraulic differential between said screening system and saidpredetermined pulp level, said screening system comprising:(a) a housingfor isolating said system from fluid contact with said pulp, andcomprising means for providing said hydraulic differential between saidpredetermined pulp level and said screening system; (b) at least onescreen member disposed within said housing for selectively andcontinuously separating said sorbent from said slurry; (c) a conduit forselectively introducing said pulp onto said at least one screen member,said pulp being urged through said conduit by said hydraulicdifferential; (d) means for returning said separated sorbent to saidtank; and (e) means for removing said separated slurry from saidscreening system.
 23. The vessel of claim 22 further comprising a pumpfor removing said separated sorbent from said tank and further whereinsaid separated slurry removing means comprises a drainage memberextending from a lower portion of said screening system housing througha wall of said tank.
 24. The vessel of claim 23 wherein said pumpintermittently removes said separated sorbent from said tank.
 25. Thevessel of claim 24 wherein said pump is periodically placed adjacentsaid screening system so that separated sorbent drops into a reservoirof said pump.
 26. The vessel of claim 22 wherein a plurality of screenmembers are used, said screen members being angularly disposed in saidhousing with respect to said predetermined pulp level.
 27. The vessel ofclaim 26 wherein said screening system includes means for vibrating saidscreen members to facilitate separation of said sorbent from saidslurry.
 28. The vessel of claim 22 wherein one end of said conduitextends to a lower portion of said tank and directs said pulp to saidscreening system.
 29. The vessel of claim 28 wherein the opposite end ofsaid conduit includes a distribution box member for uniformlydistributing said pulp into the screening system.